When it comes to basement excavation, whatever your method, one thing is clear: it’s not a DIY job. Where making mistakes in other DIY jobs, like putting up shelving or repainting walls, might amount to a costly inconvenience at the most, one wrong move in basement excavation can cause structural movement or even trigger a total collapse.
It’s definitely a job for the professionals, including an engineer and a licensed contractor. This is particularly true if you’re excavating a basement under an existing house, where staged digging, shoring and underpinning are all a must.
What is Basement Excavation, and What Does it Involve?
Basement excavation is the process of creating an underground space below a building. It’s not just a case of digging a big hole and hoping the house doesn’t fall into it, but a complex and controlled process with several important steps.
The process incorporates excavation, ground support, drainage control, and structural protection in one plan. These components combine to keep the site stable as work progresses.
Each excavation project will vary depending on the scope, and the size of the existing building. However, they largely follow the following steps:
- Site Preparation: The footprint of the basement is set out with clear lines and reference points, so all digging remains within the boundaries. Access routes are also established so machinery can move without causing damage to the property and surrounding grounds.
- Confirmation of Dark Utilities: These are cables, pipes or drains lying underground – and it’s vital to know where they are to avoid hitting them during the dig.
- Installation of Shoring and Soil Retention: Bracing is installed before walls get too deep to stay stable on their own.
- Staged Excavation: This ensures safe and manageable removal of spoil, and monitoring of any movement or settlement.
- Groundwater Management: Water is pumped out as needed to keep the base dry, keeping the ground firm and stable.
- Construction of Basement Foundation: Only when there’s a clean, stable surface should concrete be poured in. It should be left to fully cure before any additional load is added.
Is Basement Excavation Right for you?
For all everyone might like to have a basement in their home, for additional storage space or any other reason, not every home is suitable. Before you think about planning a basement excavation, here is a quick checklist you can carry out to save you the hassle of weeks of quotes that never lead anywhere:
- Existing Foundation Type: Older or more shallow footings will need more engineering input.
- Soil Type and Stability: Unstable or reactive soils usually mean more shoring and higher costs.
- Slope and Nearby Structures: A sloped block, nearby neighbours, and retaining walls can all make excavation more complicated and costly.
- Water Table and Groundwater: A high water table may call for dewatering and stronger waterproofing, to avoid groundwater flooding the excavation and softening foundations.
Planning a basement excavation and got questions? Contact us at Fraser Earthworks today.
